In situations where it is imperative that a building must not contribute fuel to a fire, only non-combustible materials should be employed. However, even if practical, the sole use of non-combustible materials will not necessarily avoid the spread of a fire generated by the burning contents of a building. Avoidance of this requires the parts of the building – materials and construction used for elements (walls, floors, etc.) – to have fire resistance. This is the term used to describe the ability of an element of building construction to fulfil its assigned function in the event of a fire without permitting the transfer of the fire from one area to another. BS 476-21 and 22: Methods for determination of the fire resistance of load-bearing and non-load-bearing elements of construction, respectively, establish a time period during which elements can be expected to perform this function. A sample must be subjected to a simulated building fire which, research has its full load during a fire for a specified period. This minimum period varies from 15 minutes up to 2 hours, depending on which part of a building it relates to and the purpose grouping or type of building it applies to.

Integrity Structural resistance to the passage of flames and hot gases. Failure occurs when cracks or other openings form, through which flame or hot gases can pass; this would cause combustion on the side of the element remote from the fire.

Insulation The ability of the construction to resist firetransmitted heat. Failure occurs when the temperature on the side of the element remote from the fire is increased generally by more than 140 °C, or at any point by more than 180 °C above the initial temperature